West German patent application No. P 29 47 018.6 discloses a resilient mounting member, in particular for mounting an internal combustion engine in a motor vehicle, which comprises a mounting core member, a support means, and at least one spring element disposed therebetween. In that arrangement, the spring element is connected for the transmission of movement to an oscillatory or amortization mass which, in the event of oscillatory movements of the mounting core member with respect to the support means, is also excited to a condition of oscillation. By virtue of this arrangement, the transmission of force or energy from the mounting core member to the support means is no longer dependent solely on the amplitude of oscillation of the mounting core member and the spring rate of the spring element, but additionally is also dependent to a degree on the frequency. Thus, at low frequencies, the transmission mode or performance substantially corresponds to that without a damper mass, while with increasing frequencies, the transmission of force also increases up to the natural frequency of the damper mass, but then falls, so that, at sufficiently high frequencies, the mode of force transmission attained is below the value determined by the static spring rate. In this resilient mounting arrangement, the damper mass can have a container which is filled with pressure liquid and/or gas and which is closed off by a diaphragm with a varying spring rate. For varying the spring rate, there is provided in the region of the diaphragm a contact surface against which the diaphragm increasingly comes to lie as the pressure in the container increases, that is to say, the spring rate is varied in dependence on the pressure in the container.
The present invention is based on the object of improving an apparatus of the general kind set forth above, such that the spring rate of the diaphragm can be varied in a desired manner, selectively, with a reduction in cost and an increase in the degree of accuracy.
Generally according to the invention, this object is achieved in that a pressure plate which is connected to an adjusting means is associated with the diaphragm. The adjusting means makes it possible for the pressure plate to be moved toward the diaphragm precisely by a predetermined amount, whereby the spring rate and the frequency of the diaphragm can be varied in the desired manner, without necessitating variations of the pressure in the container. The contour of the diaphragm and the corresponding contour of the pressure plate, which can be of a generally convex or conical configuration, are easily matched to each other so as to permit a substantially linear shift in frequency when there is a linear forward movement of the pressure plate.
The arrangement according to the invention is suitable not only for resiliently mounting internal combustion engines in motor vehicles, but for practically all situations in which the transmission of oscillatory movements in given frequency ranges is to be suppressed. The situations may also include those involving level adjustment, constant level maintenance, and damping.
Further details, features and advantages of arrangements in accordance with the invention will be apparent to those skilled in the art and described in greater detail hereinafter, with reference to a preferred embodiment illustrated in the drawing.